Unveiling the nature of three INTEGRAL sources through optical spectroscopy

Abstract

The results of an optical spectroscopy campaign performed at the Astronomical Observatory of Bologna in Loiano (Italy) on three hard X-ray sources detected by INTEGRAL (IGR J17303-0601, IGR J18027-1455 and IGR J21247+5058) are presented. These data have allowed a determination of the nature for two of them, with IGR J17303-0601 being a low mass X-ray binary in the Galaxy and IGR J18027-1455 a background type 1 Seyfert galaxy at redshift z = 0.035. IGR J21247+5058, instead, has a quite puzzling spectroscopic appearance, with a broad, redshifted H_α complex superimposed onto a ``normal'' F/G-type Galactic star continuum: these features, together with the spatially coincident extended radio emission, might suggest a chance alignment between a relatively nearby star and a background radio galaxy. These results underline the still non-negligible importance of smaller telescopes in modern astrophysics.

Based on observations collected at the Bologna Astronomical Observatory in Loiano (Italy).